Device for stamping and punching through a sheet-like workpiece

ABSTRACT

A device for stamping a depression in a sheet-like workpiece and for piercing the workpiece in the region of the stamped depression, including a punch unit and a die unit between which the workpiece can be positioned. The punch unit has a punch with a forming punch and with a piercing punch. The forming punch bears against a side of the workpiece in the region of the depression during the stamping of the depression. The piercing punch pierces the workpiece in the region of the depression. The forming punch and the piercing punch are moved along a joining axis of the device. The forming punch and the piercing punch are accommodated in a punch housing, and the forming punch and the piercing punch are driven via a common hydraulic supply system relative to the punch housing along the joining axis of the device.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of International Application No. PCT/EP2020/050246 filed Jan. 8, 2020, which designated the United States, and claims the benefit under 35 USC § 119(a)-(d) of German Application No. 10 2019 101 596.0 filed Jan. 23, 2019, the entireties of which are incorporated herein by reference.

FIELD OF THE INVENTION

The present application relates to a device for stamping and punching through a sheet-like workpiece.

BACKGROUND OF THE INVENTION

Tools for stamping a depression in a sheet-like material and for piercing the depression in one working process are known. Tools of this type have, for example, a drivable punch unit and die unit opposite the punch unit, between which the workpiece can be positioned for processing.

The stamping and piercing require, on the one hand, control of the complex working process, and a corresponding mechanism together with a controllable suitable drive arrangement.

SUMMARY OF THE INVENTION

The object of the present invention is to provide a device for stamping and piercing workpieces, as described above, by means of which working procedures can be performed with a high degree of process reliability and which is designed advantageously with respect to the working situation.

The present invention is based on a device, for example, a tool, for stamping a depression in a sheet-like workpiece and for piercing the workpiece in the region of the stamped depression, comprising a punch unit and a die unit opposite the punch unit, wherein the workpiece which can be processed by the device can be positioned between the punch unit and the die unit, wherein the punch unit has a punch with a forming punch and with a piercing punch, wherein the forming punch is designed to come to bear against a side of the workpiece in the region of the depression during the stamping of the depression, and wherein the piercing punch is configured to pierce the workpiece in the region of the depression, wherein the forming punch and the piercing punch can be moved by being driven along a joining axis of the device. The workpiece is, for example, a piece of sheet metal. The piercing is preferably effected in a material region of the workpiece which is formed by a preferably flat base of the depression. The piercing of the material or the base of the depression is effected from the side of the depression or the base at which the forming punch comes to bear against the depression or the base.

The core of the present invention consists in the forming punch and the piercing punch being accommodated in a punch housing, wherein the forming punch and piercing punch can be driven via a common hydraulic supply system relative to the punch housing along the joining axis of the device. The hydraulic supply system is preferably part of the device according to the present invention. The present invention is advantageous with respect to reduced complexity of the driving situation, in particular for that part of the punch drive which relates to the movement of the forming punch and the piercing punch relative to the punch housing.

A drive for movement of the punch housing, which is preferably additionally present on the punch unit and/or operates independently of the drive by means of the hydraulic supply system, can moreover advantageously be embodied independently of the hydraulic drive of the forming and piercing punch. The hydraulic supply system, for example, with a hydraulic pressure-generating means outside the punch housing, is preferably connected to one or preferably two or more hydraulic spaces which are present in the punch housing such that they are hydraulically separated from one another.

The hydraulic supply system is preferably configured such that the forming punch and the piercing punch can be driven independently of each other or just individually in each case or jointly with the hydraulic supply system, or can be driven at different times or after each other. For example, the forming punch and the piercing punch move, in a common driving phase, in the same or in the opposite direction of movement. The hydraulic supply system preferably serves to move the forming punch and/or the piercing punch forward, for example, in a joining direction, and backward counter to the joining direction.

Advantageously, not only is an active driven movement of the forming punch and/or the piercing punch enabled by the hydraulic supply system, it can furthermore be arranged by means of the hydraulic supply system that the hydraulic supply system applies a predeterminable counterforce to the forming punch and/or the piercing which acts counter to a movement direction of the relevant punch when the movement does not originate from the hydraulic supply system, for example, the movement is imposed from outside or non-hydraulically. The counterforce is provided, in particular, by a hydraulic fluid accommodated in a hydraulic space of the punch housing and applied to the forming punch and/or the piercing punch. Overall, a high degree of process complexity and/or a high degree of process reliability can thus be achieved, and, in particular, short-term uncontrolled situations during the process can also be avoided.

This is, for example, the case when the forming and/or piercing punch retreats when, for example, the punch housing is moved against or toward the die unit.

The piercing punch can be displaced relative to the forming punch. At least a front or die-side end section of the piercing punch is preferably accommodated inside a section of the forming punch or is surrounded externally by the latter or is guided along a corresponding wall of a recess in the forming punch. The forming punch recess is open at least on the die side so that different relative positions of the piercing and forming punches are possible depending on the driving or process situation, for example, a front die-side end section of the piercing punch protrudes at the die-side end side of the forming punch or a die-side end side of the piercing punch is retracted from the end side of the forming punch. In a non-piercing mode, the die-side end side of the piercing punch is preferably flush with the end side of the forming punch or slightly retracted therefrom.

On the die side, the piercing punch has, for example, at a base body end side of a base body of the piercing punch, such as for example of a piercing piston, for example precisely one elongated piercing section, with an end face, which protrudes from the end side of the base body and pierces the workpiece. The piercing section is preferably accommodated in a replaceable fashion on the piercing piston. The piercing punch alternatively has two or more separate piercing sections with separate end faces which protrude from the base body end side. The multiple piercing sections can be configured such that they are identical to one another or different from one another. Accordingly, with precisely one piercing section precisely one hole is pierced in the depressed region of the workpiece or, in the case of multiple piercing sections, two or more than two identical or different holes are pierced in the depressed region of the workpiece in one stroke. The piercing sections are components which are preferably separate from the base body, are, for example, replaceable and are securely accommodated in the base body or in the piercing piston of the piercing punch. A base body side, for example a forward stroke side and/or a return stroke side of the piercing punch, preferably adjoins an associated hydraulic space in the punch housing, wherein a hydraulic pressure provided by a hydraulic supply system is applied to the hydraulic space.

The hydraulic supply system preferably comprises at least one hydraulic fluid space or, for example, a reservoir in which hydraulic fluid is accommodated. The hydraulic fluid space is preferably accommodated in a structural unit which is separate or distinct from the punch unit and die unit, preferably with a housing inside which the hydraulic fluid space or the reservoir is accommodated. A piston such as, for example, an intensifier piston of a hydropneumatic pressure intensifier which acts on the hydraulic fluid is, for example, accommodated displaceably in the housing.

The hydraulic fluid space is connected hydraulically to precisely one hydraulic space of the punch unit or to multiple hydraulic fluid spaces. The hydraulic connection is preferably effected, for example, via a hydraulic connection or hydraulic line. The hydraulic connection is preferably configured as a flexible hose connection or as a rigid connection with a rigid line or with a rigid component with a housing inside which the line is present. The rigid component is preferably provided between the punch housing and a housing of the hydraulic supply system, preferably adjacent or connected thereto in each case.

A forward stroke side of a piston is a side on which a hydraulic space acts, wherein, owing to an increase in pressure in the hydraulic space, the piston can move in a forward stroke direction or along the joining axis toward the die unit. This assumes that a movement path is present for the piston in this direction, i.e. for example the piston does not contact an abutment in this direction.

Conversely, a return stroke side of a piston is a side on which a hydraulic space acts, wherein, owing to an increase in pressure in the hydraulic space, the piston can move in a return stroke direction or along the joining axis in a direction away from the die unit. The forward stroke side on a piston comprises a section on the piston which is opposite a section which belongs to a return stroke side of the piston, for example opposite sections of a piston which are oriented transversely to a piston longitudinal axis.

An advantage arises from the fact that the punch unit has a first hydraulic space and a second hydraulic space which are hydraulically separated from each other inside the punch housing. Hydraulic pressure can thus be applied to a forward stroke side and/or a return stroke side of the forming and/or the piercing punch. Either a position of the forming punch and/or the piercing punch can therefore be maintained in a fixed predetermined fashion, in particular unchanged, or a movement of the forming punch and/or the piercing punch in a desired direction along the joining axis can be predetermined. A hydraulic space can act on a forward stroke side or on a return stroke side of the forming punch or the piercing punch, or can adjoin the latter. A, for example, second hydraulic space in the punch housing can preferably act, for example, both on a forward stroke side of the forming punch and on a return stroke side of the piercing punch. The first hydraulic space in the punch housing preferably acts on a forward stroke side of the piercing punch without acting on the forming punch. A hydraulic seal, in particular, between the piercing piston and an inner wall of the punch housing is preferably formed between the first hydraulic space and the second hydraulic space. The seal can be present, for example, on the outer circumference of the moving piercing piston. The first hydraulic space and the second hydraulic space are thus reliably separated from each other hydraulically inside the punch housing. The size of the first hydraulic space and/or the second hydraulic space can preferably be changed by the movement of the forming punch and/or the piercing punch.

It is furthermore advantageous if the first hydraulic space is connected to the hydraulic supply system via a first hydraulic connection. A desired pressure level can thus be predetermined separately or controllably in the hydraulic space. The first hydraulic connection such as, for example, a hydraulic line is in particular suitable for hydraulic fluid to flow in both flow directions through the first hydraulic connection. Hydraulic fluid can thus flow into the first hydraulic space, as a result of which the volume of the first hydraulic space is increased, or hydraulic fluid can drain or flow out of the first hydraulic space, with the volume of the first hydraulic space being reduced. The first hydraulic connection preferably connects the first hydraulic space to a hydraulic high-pressure space of the hydraulic supply system.

According to an advantageous alternative of the present invention, the second hydraulic space of the punch unit is connected to the hydraulic supply system via a second hydraulic connection. The second hydraulic connection preferably connects just the second hydraulic space to a hydraulic high-pressure space of the hydraulic supply system.

The first and/or second hydraulic connection is, for example, a rigid tube line or a flexible hose line which are designed for high-pressure hydraulic operation.

Another advantage arises when the first hydraulic space and the second hydraulic space are connected to a high-pressure space of the hydraulic supply system. The first and the second hydraulic space are preferably connected to a common high-pressure space of the hydraulic supply system. The high-pressure space of the hydraulic supply system is preferably a high-pressure space in which a hydraulic high pressure of, for example, several hundred bar temporarily prevails. The hydraulic pressure can be modified, in particular lowered and increased reversibly, in the high-pressure space. The hydraulic pressure in the high-pressure space can be brought, for example, to a medium or low pressure level which is below the high-pressure pressure level. Accordingly, the high-pressure space is a hydraulic space in which a relatively high pressure prevails owing to, for example, a higher-level control unit such as, for example, a regulating unit, wherein, for example, a relatively low pressure prevails at certain times depending on the operating state.

It is particularly advantageous if the first hydraulic space of the punch unit only acts on a forward stroke side of the piercing punch. By virtue of an increase in pressure in the first hydraulic space, the piercing punch can thus be moved in a first direction of movement or in a forward stroke direction. When there is no change in the high pressure in the first hydraulic space and when no even higher pressure at the piercing punch acts counter to it, the piercing punch can be maintained in a stationary position or in its position or in the advance stroke position.

The forward stroke side of the piercing punch is preferably an axial oriented side of the piercing punch, for example, an end side of the piercing punch which faces away from the die unit. The relevant end side of the piercing punch forms, for example, a wall section, delimiting the first hydraulic space, which is movable.

The further wall sections, delimiting the first hydraulic space, are preferably fixed sections of the punch unit such as of the punch housing. The further wall sections, delimiting the first hydraulic space, preferably comprise no section of the forming punch.

According to a further advantage of the present invention, the second hydraulic space of the punch unit acts on the return stroke side of the piercing punch and on the forward stroke side of the forming punch. Accordingly, the second hydraulic space acts on a section of the piercing punch and on a section of the forming punch. The sections of the piercing punch and the forming punch preferably lie axially opposite with respect to the movement axis of the die or with respect to the joining axis, and the second hydraulic space is in between. The second hydraulic space of the punch unit is preferably formed as an annular volume on the outer circumference of part of the length of the piercing punch.

It is further proposed that the first hydraulic connection comprises a valve arrangement for opening and/or closing the first hydraulic connection. In this way, a pressure level in the first hydraulic space of the punch unit and hence a movement state of the punch unit can be influenced or predetermined. A flow of hydraulic fluid through the first hydraulic connection can thus be released or blocked, in particular, via the control unit communicating with the valve arrangement in a controllable or predeterminable fashion. The valve arrangement preferably comprises a valve such as, for example, a switchable magnetic valve.

With regard to a simple arrangement, it is advantageous if the second hydraulic connection cannot be shut off.

The second hydraulic connection in particular does not have a valve for opening and/or closing the second hydraulic connection but, in the simplest case, can be solely, for example, a hydraulic line or further line elements.

It is alternatively possible that the second hydraulic connection can be shut off and released, for example, by a valve arrangement.

According to an advantageous option of the present invention, the first hydraulic space is connected to a low-pressure space of the hydraulic supply system. The piercing punch can thus be brought hydraulically, for example, into a basic position. The piercing punch is retracted counter to the low pressure in the first hydraulic space. For this purpose, high pressure is then present in the second hydraulic space. The connection of the first hydraulic space to a low-pressure space can preferably be configured as an additional connection to the connection of the first hydraulic space to the high-pressure space of the hydraulic supply system. The first hydraulic space can thus be connected selectively to the high-pressure space or the low-pressure space via a corresponding switching of the valve arrangement.

There is moreover an advantage that the first hydraulic connection is connected to a low-pressure space of the hydraulic supply system via an interconnection.

The first hydraulic connection preferably has, at a branching point, the interconnection to, for example, a branch line which is connected to the low-pressure space.

The interconnection preferably has a valve for releasing and shutting off the interconnection.

The valve arrangement preferably comprises at least three and preferably precisely three valves. A first valve of the first hydraulic connection is present between the branching point and the first hydraulic space. A second valve of the first hydraulic connection is present between the branching point and the high-pressure space. A third valve is present in the interconnection or in the branching line or between the low-pressure space and the first hydraulic connection.

As a result, all the states relevant in practice can be configured by corresponding switched combinations by switching the three valves into in each case one of two possible states.

Accordingly, the valve arrangement for opening and/or closing a connecting section is formed between the high-pressure space and the interconnection. The connecting section is formed in particular by part of the length of the first hydraulic connection and the interconnection. The valve arrangement preferably comprises a valve for opening and/or closing the interconnection or the connecting section between the high-pressure space and the interconnection.

When the valve which is present between the high-pressure space and the connecting section is closed, the low-pressure space can be connected hydraulically to the first hydraulic space when further valves are switched to the open position in this connection.

A preferred alternative embodiment of the invention consists in the fact that hydraulic supply system comprises a hydropneumatic pressure intensifier device. The hydropneumatic pressure intensifier device is advantageous because it is a proven standard unit which is available in a completed or ready-to-use state in different alternative embodiments.

A hydraulic fluid space, present in a pressure intensifier housing and filled with hydraulic fluid, of the hydropneumatic pressure intensifier device is connected to the first hydraulic space and/or is connected to the second hydraulic space of the device. The hydropneumatic pressure intensifier device preferably comprises the low-pressure space and the high-pressure space of the hydraulic supply system.

Alternatively, a different hydraulic supply system is also possible, for example, with a hydraulic pump as a central unit of the hydraulic supply system. By means of the hydraulic pump, the hydraulic fluid is conveyed or a hydraulic high pressure and/or a hydraulic low pressure of the hydraulic supply system is provided.

Lastly, it is advantageous if a drive is provided, wherein the drive is designed to drive the punch unit in such a way that the forming punch and the piercing punch can be driven jointly relative to the die unit along the joining axis of the device or relative to the die unit. The drive comprises, for example, a drive unit. The drive or the drive unit is preferably present on the die side or is part of the punch unit. An electric drive with an electromotor is preferably present for this purpose. The punch housing can be driven by means of the drive unit relative to further components of a corresponding tool. The tool comprises, for example, so-called tongs or a so-called C-clamp.

The drive is preferably a linear drive, for example, an electric linear drive. The punch housing can be driven reversibly back and forth along the joining axis by means of the linear drive, for example, with an electromotor.

BRIEF DESCRIPTION OF THE DRAWINGS

Further features and advantages of the present invention are described in detail with the aid of an exemplary embodiment shown in the drawings of a device according to the present invention.

FIG. 1 shows a highly schematized schematic diagram of a device according to the present invention with the aid of a view in section of the device; and

FIGS. 2 to 5 show part of a schematized device according to the present invention in each case in a longitudinal section in different operating states, wherein the plane of section according to FIG. 5 is perpendicular to the plane of section according to FIGS. 2 to 4.

DETAILED DESCRIPTION OF THE INVENTION

In FIGS. 1-5, in each case part of a device 1 according to the present invention for stamping a depression 2 (see FIGS. 4 and 5) into a sheet-like workpiece 3 and for piercing the workpiece 3 in the region of the stamped depression 2 is shown. The device 1 is designed as stamping/piercing tongs 4, referred to below as tongs 4.

The tongs 4 are shown in FIG. 2 in a purely schematic fashion, with a punch unit 5 and with a die unit 6 situated opposite the punch unit 6 along a joining axis F, wherein the workpiece 3 which can be processed with the tongs 4 is held between the punch unit 5 and the die unit 6 in its flat, plane starting form, i.e. before a stamping and piercing processing step. The workpiece 3 is, for example, a sheet-metal workpiece and consists of, for example, a metal material which is just a few millimeters thick.

The punch unit 5 comprises a punch 7 with a forming punch 8 and a piercing punch 9. When it stamps the depression 2, the forming punch 8 comes to bear against a workpiece side 3 a in the region of the depression 2. After the stamping procedure, the piercing punch 9 pierces the workpiece 3 in the region of the depression 2 with an elongated piercing section 11, protruding from a base body 10 of the piercing punch 9 and comprising two piercing pins 12, 13.

The forming punch 8 and the piercing punch 9 are accommodated in a punch housing 14 which can be moved by being driven linearly in a direction R1 and in a direction R2, relative to the die unit 6, by means of a drive unit such as an electric drive 15 (see FIG. 2). The punch unit 5 is driven by means of the electric drive 15 in such a way that the forming punch 8 and the piercing punch 9 can be driven jointly with the punch housing 14 relative to the die unit 6 along the joining axis F.

Accordingly, the punch 7, or the forming punch 8 and the piercing punch 9, can be moved by being driven jointly linearly along the joining axis F in the direction R1 toward the die unit 6 and back in the direction R2 which is opposed to the direction R1.

To manage the operation of the tongs 4, a higher-order programmable control unit (not shown), for example, with a computer unit, is present.

According to the present invention, the forming punch 8 and the piercing punch 9 can be driven via a common hydraulic supply system 16 relative to the punch housing 14 along the joining axis F or the tongs 4.

The punch unit 5 preferably has a first hydraulic space 17 and a second hydraulic space 18 inside the punch housing 14. The hydraulic spaces 17 and 18 filled with a hydraulic fluid such as, for example, a hydraulic oil are hydraulically separated from each other inside the punch housing 14 by the punch housing 14 and, for example, by closed annular seals 19 circumferentially with respect to the joining axis F, on the outside of the base body 10. The annular seals 19 provide a seal against an inner side 14 a of the punch housing 14.

The first hydraulic space 17 is connected to the hydraulic supply system 16 via a first hydraulic connection 20.

The second hydraulic space 18 is connected to the hydraulic supply system 16 via a second hydraulic connection 21.

The first hydraulic space 17 and the second hydraulic space 18 are connected to a high-pressure space 22 of the hydraulic supply system 16. The high-pressure space 22 is likewise filled with the hydraulic fluid.

The first hydraulic space 17 acts on the punch 7 with respect to only a forward stroke side 9 a of the piercing punch 9 or the base body 10.

The second hydraulic space 18 acts on a return stroke side 9 b of the piercing punch 9 and on a forward stroke side 8 a of the forming punch 8.

The first hydraulic connection 20, for example, a hydraulic line such as a hydraulic hose line, has a valve arrangement 23, preferably with a valve 24 and a valve 25, for opening and/or closing the first hydraulic connection 20.

The second hydraulic line 21, for example, a hydraulic hose line, can here by way of example not be shut off or does not have a valve arrangement. The second hydraulic space 19 is always hydraulically connected to the high-pressure space 22 of the hydraulic supply system 16.

The hydraulic supply system 16 comprises a hydropneumatic pressure intensifier device 26 with a housing 27 to which indicated pneumatic lines 28, 29 are attached.

The high-pressure space 22 and a low-pressure space 31 are present inside the housing 27 of the pressure intensifier device 26. The operating principle of the pressure intensifier device 26 is explained further below.

The first hydraulic space 17 can be connected hydraulically conductively in a selective fashion to the high-pressure space 22 and/or to the low-pressure space 31 of the hydraulic supply system 16.

For this purpose, branching off from the first hydraulic connection 20, an interconnection 32 is attached to the latter for connection to the low-pressure space 31. The interconnection 32 is attached at one end to the low-pressure space 31 and at the other end to the hydraulic supply system 20. The interconnection 32 has a valve 33 for opening and/or shutting off the interconnection 32.

The valve arrangement 23 comprises the valve 25 for opening and/or closing a connecting section 20 a between the high-pressure space 22 and the interconnection 32 or a junction of the interconnection 32 with the hydraulic connection 20. The connecting section 20 a is part of the hydraulic connection 20 between the junction of the interconnection 32 and an opening, hydraulically connected to the high-pressure space 22, in the housing 27.

A pressure intensifier piston 34 and a storage piston 35 can be moved linearly in the direction R3 and back in the direction R4 inside the housing 27 of the hydropneumatic pressure intensifier device 26. The pressure intensifier piston 34 has a piston section 34 a with a larger diameter and a piston rod 36 which is connected thereto, extends centrally and has a smaller diameter than the piston section 34 a.

Compressed air is applied via the pneumatic line 28 to a pneumatic space 37, on the forward stroke side and enclosed by the housing 27, of the pressure intensifier device 26 in order to move the pressure intensifier piston 34 in displacement in the direction R3.

Compressed air is applied via the pneumatic line 29 to a pneumatic space 38, on the return stroke side and enclosed by the housing 27, of the pressure intensifier device 26 in order to move the pressure intensifier piston 34 in displacement in the direction R4.

Compressed air is applied via the pneumatic line 30 to a pneumatic space 39, on the forward stroke side and enclosed by the housing 27, of the pressure intensifier device 26 in order to move the storage piston 35 in displacement in the direction R3. The return stroke of the storage piston 35 in the direction R4 is effected by hydraulic fluid flowing into the low-pressure space 31 filled with hydraulic fluid.

A relatively high hydraulic pressure in the high-pressure space 22 is established when the pressure intensifier piston 34 is displaced in the direction R3 and is plunged into a narrowed portion 40 which has a circumferential seal 41. When the piston rod 36 is plunged into the narrowed portion 40, the wall of the narrowed portion 40 and an outer side of the piston rod 36 are hydraulically sealed with respect to each other by virtue of the seal 41 such that the high-pressure space 22 and the low-pressure space 31 are hydraulically separated at the narrowed portion 40.

The die unit 6 has a punch-side end side 6 a for the workpiece 3 to bear on one side. A die retaining means or die ring 43 which can move linearly along the joining axis F via a spring is accommodated around a central die body 42 which is fixed in position. In a basic position of the device 1 according to FIG. 2, a plane flat bearing surface is provided by the die body 42 and die ring 43 being effectively flush with the punch unit 5.

The mode of operation of the tongs 4 according to the present invention is explained below with the aid of FIGS. 2 to 5 in which the tongs 4 according to FIG. 1 are illustrated in greater detail, wherein only part of the tongs 4 is shown comprising parts of the punch unit 5 and the die unit 6.

The basic position of the device 1 is shown in FIG. 2 in which the tongs 4 are open and the punch unit 5 has been retracted in the direction R2, this being effected by the electric drive 15. Relative to an end side 5 a of the punch unit 5, the forming punch 8 is situated in a position extended in the direction R1, wherein the piercing punch 9 is lowered or withdrawn in the forming punch or is retracted in the direction R2. There is no workpiece present between the punch unit 5 and the die unit 6.

According to FIG. 3, which corresponds to the state according to FIG. 1, the tongs 4 is closed by the drive 15, wherein the workpiece 3 is fixed between the punch unit 5 and the die unit 6 or bears against the end side 6 a of the die unit 6 with one surface side and is in contact at the end with the end side 5 a on the forming punch 8 with the other surface side. The forming punch 8 is extended in the direction R1 by hydraulic pressure which is provided by the pressure intensifier device 26 via the second hydraulic connection 21. The hydraulic pressure in the second hydraulic space 18 accordingly acts on the forward stroke side on the forming punch 8 and on the return stroke side on the piercing punch 9. The piercing punch 9 is therefore retracted in the direction R2 and does not project with its piercing section 11 or with the two withdrawn piercing pins 12, 13 beyond an end side of the forming punch 8 which is opposite the end side 6 a of the die unit 6.

The intensifier piston 34 of the pressure intensifier device 26 is activated pneumatically on the forward stroke side and is extended in the direction R3 in a so-called power stroke. The piston rod 36 is thus plunged into the narrowed portion 40. Hydraulic high pressure is generated in the high-pressure space 22, wherein compressed hydraulic fluid is pumped from the high-pressure space 22 into the low-pressure space 31, which additionally functions as a storage space, via the valves 25 and 33 which are open or have been switched to be open and via the connecting section 20 a and the interconnection 32. The valve 24 is closed and shuts off the first hydraulic connection 20 to the hydraulic space 17.

In the next step, the stamping is effected (see FIG. 4) and the depression 2 is formed by means of the drive 15. All three valves 24, 25 and 33 are closed. Depending on the movement path covered by the punch unit 5 in the direction R1, a predeterminable forming depth t of the depression 2 is formed in the workpiece 3, relative to the undeformed regions of the workpiece 3. The forming depth t is, for example, up to 8 millimeters. The movement of the punch unit 5 causes the punch housing 14 to travel in the direction R1, wherein the forming punch 8 moves backward in the direction R2 relative to the punch housing 14, wherein at the same time the die retaining means or the die ring 43 moves backward in the direction R1. The end side of the forming punch 8 which faces the die unit 6 is applied to the base of the depression 2. The forming punch 8 is pushed backward in the direction R2 counter to the hydraulic pressure existing in the high-pressure space 18. As a result, by virtue of the closed valves 24, 25 and 33, when the forming punch 8 is forced backward, hydraulic fluid is forced out of the hydraulic space 18 which is becoming smaller and into the high-pressure space 22 via the hydraulic connection 21. The intensifier piston 34 and the piston rod 36 are displaced backward, counter to the power stroke pressure in the high-pressure space 22, by an amount corresponding to the amount of hydraulic fluid forced out. The hydraulic forming force prevailing in the high-pressure space 22 remains constant.

According to FIG. 5, when the electric drive 15 is not running, the piercing procedure takes place hydraulically or is determined by the hydraulic supply system 16. The forming punch 8 furthermore bears against the workpiece 3 or the depression 2 under high pressure. The piercing punch 9 with its two piercing pins 12, 13 is extended hydraulically until it abuts an abutment 45 on the forming punch 8. The pressure intensifier piston 34 is retracted by a certain amount for a short period in the direction R4 so that a sufficient volume of hydraulic fluid is present in the high-pressure space 22 in front of the piston rod 36. The repeated extension of the pressure intensifier piston 34 then takes place in the direction R3, as a result of which a power stroke occurs with a high-pressure state in the high-pressure space 22. The valves 24 and 25 are open and the valve 33 is closed. This causes hydraulic fluid to be forced at high pressure from the high-pressure space 22 and into the hydraulic space 17 via the hydraulic connection 20 and the piercing punch is extended in the direction R1. After the workpiece 3 is pierced in the region of the depression 2 by the piercing pins 12 and 13, as a result of which two holes are created in the workpiece according to the size and shape of the end side of the respective piercing pins 12, 13, the processing of the workpiece 3 is completed. The tongs 4 are then restored to the basic position according to FIG. 2.

The tongs 4 are opened by means of the drive 15, wherein the punch unit 5 travels in the direction R2. The forming punch 8 moreover is extended in the direction R1 hydraulically as far as an abutment 46 on the punch housing (see FIG. 2). The piercing piston 9 is then retracted hydraulically in the direction R2 into the basic position. For this purpose, hydraulic high pressure is established in the hydraulic space 18 which acts on the forward stroke side on the forming punch 8 and on the return stroke side on the piercing piston 9. The valves 24 and 33 are open for this purpose. The valve 25 is closed and shuts off the throughflow to the high-pressure space 22 and allows the hydraulic fluid to flow back into the low-pressure space 31.

LIST OF REFERENCE NUMERALS

-   1 device -   2 depression -   3 workpiece -   3 a workpiece side -   4 stamping/piercing tongs -   5 punch unit -   5 a end side -   6 die unit -   6 a end side -   7 punch -   8 forming punch -   8 a forward stroke side -   9 piercing punch -   9 a forward stroke side -   9 b return stroke side -   10 base body -   11 piercing section -   12 piercing pin -   13 piercing pin -   14 punch housing -   14 a inner side -   15 drive -   16 hydraulic supply system -   17 hydraulic space -   18 hydraulic space -   19 annular seal -   20 hydraulic connection -   20 a connecting section -   21 hydraulic connection -   22 high-pressure space -   23 valve arrangement -   24 valve -   25 valve -   26 pressure intensifier device -   27 housing -   28 line -   29 line -   30 line -   31 low-pressure space -   32 interconnection -   33 valve -   34 pressure intensifier piston -   34 a piston section -   35 storage piston -   36 piston rod -   37 pneumatic space -   38 pneumatic space -   39 pneumatic space -   40 narrowed portion -   41 seal -   42 die body -   43 die ring -   44 spring -   45 abutment -   46 abutment 

1. A device for stamping a depression in a sheet-like workpiece and for piercing the workpiece in the region of the stamped depression, comprising a punch unit and a die unit opposite the punch unit, wherein the workpiece which can be processed by the device can be positioned between the punch unit and the die unit, wherein the punch unit has a punch with a forming punch and with a piercing punch, wherein the forming punch is designed to come to bear against a side of the workpiece in the region of the depression during the stamping of the depression, and wherein the piercing punch is configured to pierce the workpiece in the region of the depression, wherein the forming punch and the piercing punch can be moved by being driven along a joining axis of the device, wherein the forming punch and the piercing punch are accommodated in a punch housing, wherein the forming punch and the piercing punch can be driven via a common hydraulic supply system relative to the punch housing along the joining axis of the device.
 2. The device as claimed in claim 1, wherein the punch unit has a first hydraulic space and a second hydraulic space which are hydraulically separated from each other inside the punch housing.
 3. The device as claimed in claim 2, wherein the first hydraulic space is connected to the hydraulic supply system via a first hydraulic connection.
 4. The device as claimed in claim 2, wherein the second hydraulic space of the punch unit is connected to the hydraulic supply system via a second hydraulic connection.
 5. The device as claimed in claim 2, wherein the first hydraulic space and the second hydraulic space are connected to a high-pressure space of the hydraulic supply system.
 6. The device as claimed in claim 2, wherein the first hydraulic space of the punch unit only acts on a forward stroke side of the piercing punch.
 7. The device as claimed in claim 2, wherein the second hydraulic space of the punch unit acts on a return stroke side of the piercing punch and on a forward stroke side of the forming punch.
 8. The device as claimed in claim 3, wherein the first hydraulic connection comprises a valve arrangement for opening and/or closing the first hydraulic connection.
 9. The device as claimed in claim 4, wherein the second hydraulic connection cannot be shut off.
 10. The device as claimed in claim 2, wherein the first hydraulic space is connected to a low-pressure space of the hydraulic supply system.
 11. The device as claimed in claim 3, wherein the first hydraulic connection is connected to a low-pressure space of the hydraulic supply system via an interconnection.
 12. The device as claimed in claim 8, wherein the valve arrangement for opening and/or closing a connecting section is formed between the high-pressure space and the interconnection.
 13. The device as claimed in claim 1, wherein the hydraulic supply system comprises a hydropneumatic pressure intensifier device.
 14. The device as claimed in claim 1, further comprising a drive designed to drive the punch unit in such a way that the forming punch and the piercing punch can be driven jointly relative to the die unit along the joining axis of the device. 